Electric conductor



(NoModel.)

E. E. CAMPBELL.

ELECTRIC CONDUCTOR. No. 892,108. Patented 008. 8o, 1888.

UNITED STATES PATaNT @arreso HENRY F. CAMPBELL, OF CONCORD, NEW HAMPSHIRE.

ELECTRlC CONDUCI'R.

SPECIPICATIN forming part o1' Letters Patent No. 392,103, dated October 30, 1888,

Application tiled July T, 1884. Serial No. 137,000. (No model.)

To @ZZ whom t may concern;

Beit known that I, HENRY F. CAMPBELL, of Concord, county of Merrimac, State of New Hampshire, have invented an Improvement in Electric Conductors, of which the following description, in connection with theaccompanying drawings, is a specification, like letters on the drawings representing like parts.

My invention relates to an electric conductor, having for its object to prevent disturbances arising from induction.

It has been proposed to provide theinsulating-envelope of a wire with a covering of conductive material connected with the ground or otherwise made part of a complete circuit, such covering being intended to act as a screen or shield to prevent the transmission of currents by induction to or from the inclosed wire.

In several patents granted to me December 25, 1883, and in other pending applications, I have shown and described wires or cables provided with antiinductive shields and various methods of connecting them in circuit by which extremely good protection is afforded against the effects of induced currents; and my present invention is intended to provide protection which, under some particular circumstances, is better than can readily be attained bythe construction and arrangement heretofore described and used.

The present invention consists, essentially, in a central conductor or wire inclosed in insulating material, having upon it a metallic covering or shield on which is a second insulating-covering, and outside of the latter a second metallic covering inclosing theinner covering and wire with it, so that between the inner wire and any other conductive wire which maybe in its neighborhood there are two separate metallic shields insulated frein one another and from the said inclosed wire. The said shields are connected together at the ends of the cable, so that they together constitute a complete metallic circuit, and, pref erably, the circuit of the telephones or other instruments connected by the inclosed wire will be completed by the said shields which form the return-circuit.

Figure l is a side elevation, partlyin longitudinal section, of an electric conductor provided with shields for suppressing induction in accordance with this invention, and Fig. 2 a transverse section thereof.

The main conductor a, for connecting the telephones or other instruments, T, by which communication is established, is provided with a covering, b, of insulating material of any suitable or usual character, having upon it a covering, c, of conductive material of suitable character,to prevent currents from being tra-nsinitted by induction to or from the inclosed wire. The shield or conductor c is itself provided with a covering, d, of insulating material, upon which is a second or outer conductor or shield, e, which is thus insulated from the one c throughout the length of the conductor or cable. The said conductors c and c are electrically connected together at the ends of the cable by wires 2, thus forming a complete circuit for the currents which may be engendered in the said conductor, and the circuit of the telephones T is preferably completed through the said shield-conductorsc and d, the said instruments being connected by wires 3 with the said shields.

There are certain conditions in which elec tric conductors provided with two independent shields, as herein described, are more effectively protected than by the single shields heretofore in use.

I claim- 1. An electrical conductor or cable coniposed of an insulated wire having upon it two conductive coverings insulated from one another throughout the length of the cable Vand electrically connected together at the ends thereof to form a circuit independent of the central core, substantially as described.

2. An electrical cable composed of an insulated wire having upon it two anti-inductive shields composed,1nainly,of parainagnetic inaterial insulated from one another, except at the ends of the cable,where they are connected to constitute a metallic circuit extending the entire length of the cable, substantially as dcn scribed.

In testimony whereof I have signed my naine to this specification inthe presence of two suhscribing witnesses.

HENRY F. CAMPBELL,

Vitnesses:

Jos. I). Livnmronn, W. H. SIcsroN. 

